1. Field of the Invention
The present invention relates to a substrate having fine lines, and a method for manufacturing the same. Particularly, the invention relates to a configuration in which the fine lines are wires provided on the substrate, and a configuration in which a technique for providing the fine lines are applied to an electron-source substrate and an image forming apparatus.
2. Description of the Related Art
FIG. 14A is a plan view illustrating a surface-conduction-type electron emitting device. FIG. 14B is a cross-sectional view taken along line B-Bxe2x80x2 shown in FIG. 14A. In FIGS. 14A and 14B, there are shown an insulating substrate 2, a conductive film 15, electrodes 11 and 12, and an electron emitting portion 16.
FIG. 15 is a schematic diagram illustrating the configuration of an image display apparatus which uses electron emitting devices 100, each such as the one shown in FIGS. 14A and 14B. In FIG. 15, there are shown a substrate 151, an external frame 152, and a faceplate 156 having an image forming member 154 disposed thereon.
An envelope (air-tight container) 157 for maintaining the inside of the image display apparatus in a vacuum by sealing respective connecting portions between corresponding ones of the external frame 152, the substrate 151 and the faceplate 153 using a bonding material (not shown), such as a low-melting-point glass frit or the like, is provided.
A substrate 158 is fixed on the substrate 151. The electron emitting devices 100 whose number equals Nxc3x97M (N and M are positive integers equal to or more than 2, appropriately selected in accordance with the number of pixels for displaying an image) are formed by being arranged on the substrate 158. Each of the electron emitting devices 100 is connected to corresponding ones of wires 159 and 160, each made of a conductive film.
In FIG. 15, M column-direction wires 159 and N row-direction wires 106 (also called xe2x80x9cmatrix wiresxe2x80x9d) are provided. Insulating layers (not shown) are provided at intersections of the row-direction wires 160 and the column-direction wires 159, so that the row-direction wires 160 are insulated from the column-direction wires 159.
In order to form the above-described image display apparatus, it is necessary to form and arrange a large number of row-direction wires 160 and column-direction wires 159.
In order to form and arrange a large number of thick row-direction wires 160 and column-direction wires 159, for example, Japanese Patent Application Laid-Open (Kokai) No. 8-34110 (1996) discloses a method of using a printing technique which is relatively inexpensive, does not require a vacuum apparatus and the like, and can deal with a large area.
In addition to the above-described surface-conduction-type electron emitting devices, for example, spindt-type electron emitting devices, each having a cone-shaped electron emitting portion, and MIM(metal-insulator-metal)-type electron emitting devices have been known as the electron emitting devices. By being combined with a phosphor emitting light by electrons emitted from an electron emitting device, the electron emitting device can be used as an image display device. In addition to the above-described electron emitting devices, for example, EL (electroluminescent) devices have been known as image display devices. A configuration in which an image is displayed by using very small integrated mirrors as image display devices and controlling reflection of light by the very small mirrors has also been known. A configuration in which an image is displayed using liquid-crystal devices as image display devices has also been practically used widely.
Japanese Utility Model Application Laid-Open (Kokai) No. 5-38874 (1993) discloses another background technique. This application discloses a technique in which in order to connect two conductive films facing each other, resistive films are superposed on respective end portions of the two conductive films. Particularly, in order to prevent growth of cracks in each of the resistive films at a step portion of superposition into a single large crack, the end portion of the conductive film is formed with a crooked line comprising lines or curves, having a saw-tooth shape, a comb-like shape, a wavy shape or the like.
The inventors of the present invention have studied a configuration in which, when forming fine lines on a substrate, the fine lines are obtained according to exposure and development. More specifically, a photosensitive material is used for forming fine lines, and the fine lines are obtained by selectively exposing predetermined regions followed by development. The studies by the inventors of the present invention have cleared that fine lines obtained according to this approach tend to peel from the substrate particularly at end portions of the fine lines in the longitudinal direction.
According to the present invention, the problem that fine lines are peeled when an exposure/development process is included in processes for forming the fine lines is solved.
That is, in a substrate including fine line, the fine line is obtained according to a fine-line forming process including a process of projecting light from above the substrate onto predetermined region on a photosensitive material provided on the substrate and a developing process after the light projection process. A narrow-width portion is provided at an end portion of the fine line in a longitudinal direction of the fine line. A width of the narrow-width portion is smaller than a width of a portion adjacent to the narrow-width portion.
According to the invention, it is possible to suppress peeling of end portions peculiar to fine lines formed according to the fine-line forming process including the exposure process and the developing process.
The following two configurations have been known as configurations in which unnecessary portions are removed by forming a latent image by projecting light onto predetermined regions and developing the latent image. Both of the two configurations may be applied to the present invention. In one of the two configurations, a latent image is formed by portions where light having an intensity sufficient enough for forming a latent image has been projected, and portions where light having an intensity insufficient for forming a latent image has been projected are removed by development. In another configuration, a latent image is formed by portions other than portions where light having an intensity sufficient enough for being removed by development has been projected, and portions other than portions where the latent image is formed are removed by development. The latent image in this specification corresponds to portions which are not removed even by development, and therefore is not limited to an invisible image.
The present invention is particularly suitable when the fine line is obtained by being heated after the developing process, because it is considered that a stress generated when the size of the material obtained by development changes due to the heating is a great factor for peeling of end portions. The present invention is particularly suitable when the fine line obtained by the heating has a width smaller than a width of the material after the developing process and before the heating.
The present invention is particularly suitable when the fine line obtained by the heating has a thickness equal to or more than 5 xcexcm.
The present invention is particularly suitable when the material immediately before projecting the light has a thickness equal to or more than 8 xcexcm.
The fine line according to the present invention may be suitably adopted as wire.
The present invention is particularly suitable when the material is a metal paste, or when silver is contained as a main component for providing a conductive property.
A configuration in which the end portion has a cut provided from a distal end of the end portion such that the end portion is divided into at least two portions, or a configuration in which the end portion is chamfered from a distal end of the end portion may also be preferably adopted. The above-described cut or chamfer is not always formed by first providing a shape in which the cut or the chamfer is absent, and then performing cutting or chamfering. A shape in which the cut or the chamfer is present may be simultaneously formed according to light projection and subsequent development.
It is particularly preferable that a length of the narrow-width portion in the longitudinal direction is at least half a width of a portion adjacent to the narrow-width portion.
A configuration in which a portion of the end portion where the width gradually decreases toward a distal end of the end portion is provided as the narrow-width portion may be preferably adopted.
According to the present invention, a method for manufacturing a substrate having fine line includes a fine-line forming step for forming the fine line. In the fine-line forming step, a narrow-width portion is provided at an end portion of the fine line in a longitudinal direction, and the fine line is formed so that a width of the narrow-width portion is smaller than a width of a portion adjacent to the narrow-width portion. The fine-line forming step includes a step of providing a photosensitive material onto the substrate, a step of projecting light from above the substrate onto predetermined region on the material, and a developing step after the light projection step.
According to this method, it is possible to preferably manufacture a substrate having fine lines whose end portions hardly peel. It is particularly preferable to simultaneously form the shape of the end portion according to the light projection step and the developing step.
The present invention also provides an electron-source substrate including the above-described substrate and electron emitting device provided on the substrate. The fine line is wire for supplying the electron emitting device with a signal for driving the electron emitting device.
A configuration in which a plurality of the electron emitting devices are provided, and the plurality of electron emitting devices are arranged in the shape of a matrix, and a plurality of the wires perform matrix connection of the plurality of electron emitting devices arranged in the shape of the matrix may be preferably adopted.
The present invention also provides an image display apparatus including the above-described substrate and image display devices, in which the fine lines are wires for supplying the image display devices with a signal for driving the image display devices.